Mattresses typically include an inner construction covered by a mattress sack. The mattress sack generally includes top and bottom panels which are interconnected by side panels. The sack usually is secured to the inner construction by a flange which is secured to the periphery of one of the top and bottom panels and which is connected to the inner construction using hog rings or the like. The inner construction typically includes springs of known configurations. The top and bottom panels may be sewn directly to the side panel, or joined with border tape or the like.
The flange material is usually affixed to the edges of a top or bottom panel at the same time as the edges of the panel are cut and stitched. This process utilizes a sewing machine adjacent a table upon which the mattress panel rests. While in the past, this process was primarily a manual operation, efforts have been made in more recent times to automate this process. Early attempts held the mattress panel stationary while propelling the sewing machine around the circumference of the mattress panel. More recent efforts in this regard have held the sewing machine stationary while manipulating the mattress panel on an air table. Examples of such apparatus are found in U.S. Pat. Nos. 5,529,004 (assigned to the Assignee of the present application), Publication No. W095/25194 (assigned to the Assignee of the present application), U.S. Pat. No. 5,560,308 and U.S. Pat. No. 5,367,968.
Problems encountered in all of these systems, and partially solved in some of the foregoing patents, include proper alignment of the edge of the mattress panel with the sewing needle, and proper rotation of the mattress panel around a corner to produce a rounded, evenly cut corner with the desired radius and stitching, and proper alignment of the flange material.
It is highly desirable to automate as much of the process as possible and to minimize the amount of manual labor required for sewing the mattress panels. Automation saves labor costs and minimizes injury to workers, produces a higher level of accuracy and provides reproducibility to render a more uniform look to the finished product.
Despite efforts to improve accuracy and to minimize worker participation, there is still room for improvement in both areas. In particular, some of the foregoing existing apparatus still require manual guidance of the sewn edge of the panel as it passes through the sewing machine, particularly at the end of the sewing cycle. In addition, the foregoing existing apparatus still require that the panel be manually removed from the table or sewing area at the end of the stitching cycle.
Therefore, it is one object of the present invention to more fully automate the process of stitching the edges of a mattress panel and attaching the flange.
It is another object of the present invention to further increase the accuracy and reproducibility of the stitching of the edges of the top and bottom panels of a mattress sack, and the attachment of the flange.